: CDC believes that the current scientific evidence does not support the hypothesis that MMR, or any combination of: vaccines, cause the development of autism, including regressive forms of autism. A suspected link between MMR vaccine: and autism has been suggested by researchers and some parents of children with autism. Often symptoms of autism are: first noted by parents as their child begins to have difficulty with delays in speaking after age one. MMR vaccine is first: given to children at 12 to 15 months of age. Therefore, children an apparent onset of autism within a few weeks after: MMR vaccination may simply be an unrelated chance occurrence.

: An extensive study of the evidence was recently conducted in the United Kingdom. The British Committee on Safety of: Medicines convened a "Working Party on MMR Vaccine" to conduct a systematic review of reports of autism,: gastrointestinal disease, and similar disorders after receipt of MMR or measles/rubella vaccine. The National Childhood: Encephalopathy Study (NCES) was examined to see if there was any link between measles vaccine and neurological: events. The researchers in England found no indication that measles vaccine contributes to the development of long-term: neurological damage, including educational and behavioral deficits (Miller et al 1997). A more recent epidemiological study: also found no association between MMR vaccine and autism (Taylor et al. 1999). This study compared rates of autism: between children who received the MMR vaccine and children who did not. The results found no difference in rates of: autism between the two groups.

: 2. What about the study by Dr. Andrew Wakefield, of the Royal Free Hospital in the United Kingdom?

: Current scientific evidence does not support the hypothesis that the MMR vaccine, or any combination of vaccines, causes: the development of autism, including regressive forms of autism. This includes the research conducted by Dr. Wakefield.

: The Wakefield Study

: This study was conducted in 1998 and looked at whether the existence of the measles virus from the MMR vaccine could: cause bowel disease and, in turn, cause autism. The authors reviewed reports of 12 children with bowel disease and: regressive developmental disorders, mostly autism. In 9 of the cases, the child's parents or pediatrician speculated that the: MMR vaccine had contributed to the behavioral problems of the children in the study.

: This study was reviewed by an expert committee from the UK Medical Research Council (MRC). The Council concluded: there is no evidence to link the MMR vaccine with autism. On April 3, 2000 the MRC issued a new report confirming its: earlier conclusion; MMR has not been linked with inflammatory bowel disease in autism. A copy of this research report: can be found in the appendix and is also available at the MRC web site, http://www.mrc.ac.uk

: Limitations of Dr. Wakefield's Study

: 1. The study used too few cases to make any generalizations about the causes of autism; only 12 children were included in: the study. Further, the cases were selected by researchers and may not be representative of many cases of autism.

: 2. There were inadequate groups of control children. As a result, it is difficult to determine whether the bowel changes: were similar to changes in normal children, or to determine if the rate of vaccination in autistic children was higher than in: the general population.

: 3. The study did not identify the time period during which the cases were identified.

: 4. In at least 4 of the 12 cases behavioral problems appeared before the onset of symptoms of bowel disease; that is, the: effect preceded the proposed cause. It is unlikely, therefore, that bowel disease or the MMR vaccine triggered the autism.

: : 3. Would it be safer to separate the MMR vaccine into its individual components--in other words, give children three: separate shots, at different times (e.g., six months or one year apart), instead of one combined shot? Why do we have to: use the combined vaccine?

: There is no scientific research or data to indicate that there is any benefit to separating the MMR vaccine into its: individual components. This idea is not based on any published evaluation of the effect(s) it may have on children. In fact,: splitting the MMR vaccine into three separate doses may be harmful because it would expose children unnecessarily to: potentially serious diseases. For instance, if rubella vaccine were delayed, 4 million children would be susceptible to rubella: for an additional six to 12 months. This would potentially allow otherwise preventable cases of congenital rubella syndrome: (CRS) to occur. Infection of pregnant woman with "wild" rubella virus is one of the few known causes of autism. Thus, by: preventing infection of pregnant women, rubella vaccine also prevents autism.

: : 4. Should a younger sibling, or a child of someone who suffered autism be vaccinated with MMR or other vaccines? : Current scientific evidence does not support the hypothesis that MMR, or any combination of vaccines, cause the: development of autism, including regressive forms of autism.

: While family history may need to be considered in specific circumstances, no contraindications to vaccination exist solely: on this basis. Genetic susceptibility to severe events is worthy of further research. A younger sibling or the child of: someone who suffered a vaccine adverse event usually can, and should, safely receive the same vaccine. This is: especially true since the large majority of adverse events after vaccination are local reactions and fever, which do not: represent a contraindication.

: Due to the general safety of vaccines, and the rarity of serious vaccine adverse events, it is extremely difficult to study: whether a subgroup (e.g., family members) are actually at increased risk compared with the general population. The one: exception is an increased risk of neurologic events--primarily febrile seizures--after vaccination with DTP vaccine and: measles-containing vaccines (MCV). The risk increases if any of these have previously occurred in immediate family: members. Considering the rare occurrence of these events after DTP and MCV vaccination, the generally benign: outcome of febrile convulsions, and the risk of pertussis and measles to unvaccinated people and the general population,: the Advisory Committee on Immunization Practices concluded that a history of convulsions in siblings or parents should: not be a contraindication to pertussis or measles vaccination. Special care in the prevention of post-vaccination fever may: be warranted in children with a family history of seizures, however. Oral polio vaccine (OPV) is contraindicated when: there is a family member with immune-deficiency since OPV can spread to family contacts.

: : 5. Should we delay vaccination until we know more about the negative effects of vaccines? : There is no convincing evidence that vaccines such as MMR and hepatitis B cause long term health effects. On the other: hand, we do know that people will become ill and some will die from the diseases these vaccines prevent. Discontinuing a: vaccine program based on unproven theories would not be in anyone's best interest. Isolated reports about these vaccines: causing long term health problems may sound alarming at first. However, careful review of the science reveals that these: reports are isolated and not confirmed by scientifically sound research. Detailed medical reviews of health effects: reported after receipt of vaccines have often proven to be unrelated to vaccine but related to other health factors.: Because these vaccines are recommended widely to protect the health of the public, research into any theory about their: safety is important to follow and further investigate. Several studies are currently underway to further investigate whether: suggested long term effects are real or false signals.

: 6. I have heard that measles virus was found in specimens from intestines of children with autism? Have these data been: reviewed by other scientists?

: The recently released finding has not yet been published in a scientific journal. This means that it has not been reviewed: by other medical experts, before and after publication, to assure the methods of the study are sound. No other laboratories: have had similar findings. Such tests should be repeated by several laboratories to ensure accurate results. Several: renowned measles laboratories have offered to duplicate the tests in order to validate the results. This is a typical: procedure that is followed in medical research.

: 7. What if multiple laboratories confirmed the presence of measles virus in specimens from the intestines of children with: autism? Would that indicate that measles causes autism?

: Even if measles virus were consistently shown to be present in intestinal specimens of children, this would not conclusively: indicate that measles causes autism. It is possible that the measles virus persists in the intestines of children with autism,: i.e, the measles virus in the intestine is a side effect of autism, not a cause. In addition, in order to implicate measles virus: as a cause of autism, it would be important to show that measles virus is not present in the bowel of healthy children who: are of the same age as the autistic children and have the same history of measles infection and the same vaccination: status. Also, there is no scientific evidence to show how intestinal inflammation with measles virus would cause the: chronic neurological and behavioral difficulties seen with autism.

: 8. What if measles virus is shown to be associated with autism? Would that mean we should stop vaccinating against: measles?

: If measles virus is shown to be associated with autism, it would be most likely that the wild measles virus would be a: greater cause of autism than vaccine virus. Therefore, it is likely that in preventing wild measles virus infections, we also: would be reducing the total number of cases of autism. People infected with wild type measles virus develop severe: infections. Vaccination exposes the child to a weaker measles virus and prevents the complications of these severe: infections. As an example, a severe degenerative infection of the brain (sub-acute sclerosing panencephalitis or SSPE): can occur following wild - type measles virus infection. Vaccine virus does not cause this severe degenerative infection: and vaccination programs in the United States have virtually eliminated such complications by controlling measles.